Impact of the loading effect on CD control in plasma etching of Cr photomasks using ZEP 7000 resist

Abstract

As requirement of CD uniformity on photomask continue to tighten with advanced logic and memory devices, new process technologies will be needed to be developed to address the gap of process capability. For instance, a less than 20 nm CD range will be required on a 0.18 micrometer generation logic devices with a nominal field area of 120 X 120 mm. New technologies such as high energy e-beam write (to reduce forward scattering), advanced e-beam photoresist and plasma etch processes are currently being developed to achieve such stringent CD uniformity specifications. One of the key issues of plasma etch technology is related to microloading effects which accounts for a major portion of CD budgets. In this work, an engineering test mask was designed to identify etch microloading mechanisms and to improve performance of a standard Magnetic-Enhanced Reactive Ion Etch (MERIE) process. Additional comparison of CD microloading was also made with an Inductively-Coupled Plasma (ICP) etch process.